As illustrated by Example 34 of U.S. Pat. No. 4,077,930 to Lim, et al., a self-inverting emulsion having a viscosity of 2000 cps and containing a polymer derived from acrylamide, diallyldimethylammonium chloride (DADMAC) and 2-methacryloylethyltrimethyl ammonium methosulfate, is known. This emulsion is produced by a polymerization procedure in the presence of a high HLB emulsifier.
One of the major problems in acrylamide, diallyldimethylammonium chloride polymerizations is incomplete incorporation of the latter, i.e. of the DADMAC monomer into the acrylamide polymer. This is due to the fact that acrylamide is considerably more reactive than DADMAC, and therefore tends to self-polymerize rather than react with the cationic monomer. As a result, one or more of the following results: the DADMAC monomer is wasted; it is difficult to predict the composition of the polymer; and/or undesireable charge distributions result. Accordingly, there is an apparent need for a process for effecting an improved incorporation of DADMAC into an acrylamide polymer. An improved process of this kind would be particularly beneficial because it would produce an inverse emulsion polymer of DADMAC of increased viscosity and improved stability. Furthermore, when prepared by the procedure disclosed in the Lim, et al. U.S. Pat. No. 4,077,930, a typical emulsion is relatively unstable, having about 5-6% v/v oil separation and about 5-10% v/v cream after one month at 50.degree. C. Therefore, a process that is capable of yielding an increased DADMAC incorporation would be especially useful if it also produced an inverse emulsion polymer having a very high degree of thermal stability. For example, less than 2% v/v oil separation and less than 2% v/v cream after one month at 50.degree. C. Also it is beneficial to keep the product viscosity below 1000 cps.